This invention concerns a method to regulate an illuminating range of a motor vehicle in which signals are measured at a position on a front axle and at a position on a rear axle, which signals depend upon a relative position of a motor vehicle body, or chassis, to the front and rear axles, with a difference between these signals being formed as a difference signal, with the resulting difference signal, as a nominal-value signal, being filtered to a first mean, or average, value, with a time for the first average-value formation being determined by a first filter time constant, and with positions of adjusting elements being regulated when the first, filtered, nominal-value signal deviates from a predetermined, or set, value and an apparatus for regulating the illumination range of a motor vehicle.
A method and an apparatus to regulate the illumination range of a motor vehicle of this type is known from German Offenlegungsschrift DE OS 31 10 094 A1.
Sensors which measure the relative position of a body, or chassis, of a motor vehicle to motor-vehicle axles or motor-vehicle wheels, are coupled to an analog multiplexer which feeds signals from the sensors via an analog/digital converter to a microprocessor. A filtering of the available signals results, while in a definite, or set, time period, a mean, or average, value formation of these signals is carried out. For this purpose, the number of measured values to be included is set, or predetermined. From the average values then for each sensor pair, that is, a respective front axle and rear axle sensor, a difference signal is formed that corresponds to a headlight adjustment value. Each of these difference signals is fed to a digital/analog converter which is coupled via a respective subsequent operational amplifier with a headlight adjustment apparatus. Depending upon the sense (plus or minus) of the difference signals, the adjusting elements are thereby moved forwardly or backwardly and headlight position registers in the microprocessor count upwardly or downwardly.
It has proven to be particularly disadvantageous that inclination changes of the motor vehicle body not attributable to changes in loading or road surface unevenness are not recognized so that because the measured signals from the axle sensors corresponding to inclination changes during, for example, driving about a curve, the average-value formation is falsified, whereby, for example, after driving about a curve false adjustments of illumination range are present which can lead to a blinding of oncoming traffic o to reduction in safety whereby dangerous situations during operation of a motor vehicle are brought about.
It has proven to be particularly disadvantageous with the known device that four sensors are provided to determine the relative position of the motor-vehicle body to the motor-vehicle axles or motor-vehicle wheels which are coupled via an analog-multiplexer to a microprocessor, whereby an embodiment associated with high costs result which demands additionally an increased expenditure of time and costs upon manufacture and mounting.
An object of this invention is to provide regulation of a light distance (illumination) range of a motor vehicle which is uncomplicated and cost effective and which recognizes those inclination changes of the motor-vehicle body which are not attributable to changes in load or in road surface unevenness and thereby avoids false adjustments caused by these inclination changes during regulation of the illumination range.